Pointing devices are widely used to support human-computer interaction. Current pointing devices allow the user to move an on-screen cursor using movements of their arm and wrist (e.g. in the case of computer mouse devices) or their fingers and thumb (e.g. in the case of touch-pads and trackballs). Most users prefer mouse devices for regular use on a desktop setting, as mouse devices are generally considered to be more comfortable for extended use than other alternatives. Pointing devices can be characterized as providing indirect interaction, as the user interacts with a device to control an on-screen cursor, and the on-screen cursor manipulates objects, buttons or controls in the user interface. This can be distinguished from direct interaction methods such as touch-screens, where the user's touch directly manipulates the user interface.
Humans are naturally dexterous and use their fingers and thumbs to perform a variety of complex interactions with everyday objects to a high precision. Certain input movements and gestures are more easily accomplished by using the fine motor control of one or more fingers and thumb, rather than the gross motor control of the arm and wrist. For example, moving an object a fraction of a millimetre, or tracing an accurate path (for example, when drawing or writing) can be more quickly, easily and exactly accomplished by using fingers and thumb rather than with the arm and wrist. As a result of this, there is increasing interest in multi-touch interaction techniques, where the user interacts with a graphical user interface using more than one finger to control and manipulate on-screen objects.
Multi-touch interaction can be intuitive for users in a direct interaction environment (e.g. when used with touch-screens) as the users can directly visualize the effect of moving their fingers on the display. For indirect interaction, the use of multi-touch is less prevalent. For example, multi-touch enabled touch-pads can be used to provide limited indirect multi-touch input to a user interface, for example to control scrolling. However, for indirect interaction, multi-touch techniques are less intuitive and less accurate. The gestures that can be enabled by such a touch-pad are limited as the users cannot readily visualize how the multi-touch inputs are being interpreted in the user interface. As a result of this, the accuracy of the multi-touch input is reduced and only a small number of multi-touch gestures can be supported with a reasonable reliability.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known indirect interaction devices.